We propose a low bit-rate coding algorithm for wireless communication based on multi-stage hierarchical vector quantization, motion compensation and differential pulse code modulation. Our method adapts bit allocation...
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We propose a low bit-rate coding algorithm for wireless communication based on multi-stage hierarchical vector quantization, motion compensation and differential pulse code modulation. Our method adapts bit allocation to spatial and temporal correlation. Conventional schemes based on the discrete cosine transform (DCT) need a large amount of computation on both encoding and decoding. On the other hand, our proposed method consists of addition, subtraction and shift operation. It does not use multiplication. It can decode in real time on a conventional serial processor. Encoding by vector quantization (VQ), however, consumes a large amount of computation. We developed a new LSI to accelerate VQ. Our scheme can send 10 frames of QCIF video sequences through a 29.2 kbps line. The quality of reconstructed image is over 30 dB.
Conventional correlation based single-user techniques for direct sequence code division multiple access (DS-CDMA) wireless communication systems are susceptible to performance degradation due to interference from othe...
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Conventional correlation based single-user techniques for direct sequence code division multiple access (DS-CDMA) wireless communication systems are susceptible to performance degradation due to interference from other users. Previous research has focused on development of several multiuser techniques where information about multiple users is used to improve performance for each individual user. Due to performance benefits of these methods, they are attractive candidates for implementation in future cellular systems. In this paper we present an error analysis of fixed point implementation of some of these techniques.
We have previously introduced modulation and coding schemes that permit the simultaneous reception of a basic message stream by receivers with a wide range of capabilities and an additional message stream by more capa...
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We have previously introduced modulation and coding schemes that permit the simultaneous reception of a basic message stream by receivers with a wide range of capabilities and an additional message stream by more capable receivers. In a tactical military application, the basic message may represent a voice message, while the additional message may correspond to a digitized image. We investigate adaptive modulation and coding techniques based on our previous schemes, and we apply the adaptive techniques to a cellular communication system that employs direct-sequence spread-spectrum multiple access, also known as code-division multiple access (CDMA). In a cellular CDMA system each mobile terminal experiences variations in both the received signal strength and the interference. We show that by adapting the parameters of the modulation and coding to the signal-to-interference ratio, the throughput can be increased for the additional message while maintaining an acceptable error rate for the basic message.
The 3-state and 4-state Markov models are proposed as the long-bursting error possibility models of mobile channels. The coding and decoding of simple convolutional codes and the method of interleaving are combined. T...
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The 3-state and 4-state Markov models are proposed as the long-bursting error possibility models of mobile channels. The coding and decoding of simple convolutional codes and the method of interleaving are combined. The error-correcting performance of interleaved convolutional codes in nine different channels with different modulation styles, vehicle speeds, and different information transmitting rates is simulated and researched. In addition, the above is compared with former research work on BCH codes and analyzed. Some significant conclusions are obtained.
Summary form only given. The operation, administration, and maintenance (OAM) of a transport network require the generation, transmission, and detection of OAM signals that are related to each network layer. In the mo...
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ISBN:
(纸本)1557525293
Summary form only given. The operation, administration, and maintenance (OAM) of a transport network require the generation, transmission, and detection of OAM signals that are related to each network layer. In the modelled system Gold codes have been applied for transport of the OAM-signals at channels, which have been modulated externally (by Mach-Zehnder modulators) at different modulation levels in order to characterize the influence of the modulation depth. The simulation has shown the feasibility of CDMA for transport of OAM-signals with a bandwidth up to l0-kbit/s per optical carrier in transparent optical networks with minimised distortion of the high speed data stream.
We formulate differential pulse code modulation (DPCM) for image compression as the minimization of a quadratic cost function. Non-causal interpolation error image in lieu of causal prediction error image can be coded...
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We formulate differential pulse code modulation (DPCM) for image compression as the minimization of a quadratic cost function. Non-causal interpolation error image in lieu of causal prediction error image can be coded in this fashion providing efficient compression. We implement the optimization process through the dynamics of cellular neural networks (CNNs). Two CNNs, one of them operated in binary mode and the other in gray level mode, are used in the coding stage. The first CNN creates an optimum differential image while the other tries to create a replica of the reconstructed image of the receiver. Decoding is realized by another gray level mode CNN fed by the differential image.
We consider a collision channel (Massey and Mathys 1985) with additive white Gaussian noise (AWGN) and slow fading. We assume that data on a collided slot are completely lost. Caire et al. (1998) proposed a combinatio...
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We consider a collision channel (Massey and Mathys 1985) with additive white Gaussian noise (AWGN) and slow fading. We assume that data on a collided slot are completely lost. Caire et al. (1998) proposed a combination of signal-space coding and slow time-frequency hopping for this channel. Code vectors (or equivalently, signals) are points in a D-dimensional real Euclidean space. The main idea is that, under certain conditions on the signal-space code and provided that signal points are transmitted so that their D components belong to different time-frequency slots, even if k
This paper examines some of the complexity issues arising in the real time implementation of the symbol timing subsystem of a narrowband wireless modem. The modem prototype has been designed for 4 kHz channels in the ...
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This paper examines some of the complexity issues arising in the real time implementation of the symbol timing subsystem of a narrowband wireless modem. The modem prototype has been designed for 4 kHz channels in the 220-222 MHz land mobile band. In an effort to achieve high bandwidth efficiency, the modem architecture employs transmitter diversity, pilot symbol assisted modulation, and trellis coded modulation. An experimental, non-real time system has been implemented and extensively field tested demonstrating bandwidth efficiencies in excess of 3 bits per second per Hz. The work on this project is focused on the real-time implementation of the baseband receiver functions using the Texas Instruments C54/spl times/ fixed point digital signal processor. Here we report on some of the performance/complexity tradeoffs present in the design of a DSP implementation of the digital filter and square symbol timing recovery algorithm.
A decision feedback receiver/decoder for IS-95 CDMA uplink in multipath and Rayleigh fading is presented. The receiver/decoder design shows a consistently better performance than conventional receivers that use the sa...
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A decision feedback receiver/decoder for IS-95 CDMA uplink in multipath and Rayleigh fading is presented. The receiver/decoder design shows a consistently better performance than conventional receivers that use the same decoding metric. Results are presented for both coherent and noncoherent detection.
We consider the design of multiuser receivers for multicarrier direct-sequence CDMA communications over fading channels. We present a class of spreading codes that enables the simple despreading-combining (DC) receive...
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ISBN:
(纸本)0780351487
We consider the design of multiuser receivers for multicarrier direct-sequence CDMA communications over fading channels. We present a class of spreading codes that enables the simple despreading-combining (DC) receiver to achieve the performance of an optimum multiuser linear receiver. These codes are shown to be optimum for independent fading channels under the code design criterion derived. Simulation results are provided to demonstrate the significant gains in performance and simplicity due to the proposed techniques.
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